Automatic telephone system



April 30, 1935. N. H. sAuNDERs AUTOMATIC TELEPHONE SYSTEM Filed Feb. 5.1953 4 sheets-sheet 1 \Q\\\w\\w\ s fr. i r I m d QW. xnkN MN SM. .H l Wf nl.. .N @n Lw TI f @www Q .n ...l p ww Mv A; bw M4 Qi lljwl R j Q1 I..l ME ww vw @w ww Q ma .I www. @j m F mf. S, Q. NM .ww U 1 M ,y E u h MEQ\r.|| m. w .a MTL Q NN wh. QSQQ SG Nkw .QN S- Q April. 30, 1935. N. H.sAUNDl-:Rs I v 1,999,788 AUTOMATIC TELErHoNE SYSTEMv File'd Feb. s, 19554 sheets-sheet 2 April 30, 1935. N. H. sAuNDERs AUTOMATIC TELEPHONESYSTEM Filed Feb. 5, 1933 4 .Sheets-Sheet 5 www mwN

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l AUTOMATICv TELEPHONE SYSTEM Filed Feb. s, 1955 4 sheets-sheet 4 www 'Patented Apr.- 30, 1935v n r., villages. d" type is generally known as acommunity auto` UNITED STATES f PATENT oFFicE i AUToMA'rrcfrELEPnoNESYSTEM Norman H. Saunders, Chicago, Ill., assignor to AssociatedElectric Laboratories, Inc., Chicago, Ill., a corporation-of DelawareApplication February 3,

30 Claims.

This invention relates in general to automatic telephone systems, ybutmore in particular to small systems suited for installation in towns orAn automatic telephone system of this matic exchange or C. A; X. Such atelephone system may be of about'fty lines capacity, more or less, andthe lines would-ordinarily be of various types.- such as commonbatterylines and local battery lines, full metallic lines, and grounded lines.AThere usually also would 'be a considerable proportion of party lines,and some of these party lines may have so many subscribers onk them thatselective ringing is impracticable, making it necessary to resort tocode ringing. A community automatic exchange generally also has' to betrunk connected with one or more exchanges in adjacent cities, which maybe either of the manual or automatic type. Provision must therefore bemade for trunking calls to'manuai rexchanges or for dialling into otherautomatic exchanges'.

The objectl of the present invention is to producer a novel and improvedcommunity auto-1 matic exchange of the foregoing character. A specialobject is to provide for taking care of all of the various types ofservice that ordinarily are met with inthe situation which is outlinedabove, so that a single type of exchange can be manu iactured and soldforf'usefin4 any community ren gardless of the particular requirementsof that community. The exchange which l have de signed may therefore befittingly termed a unas versal C. A. X. A further object of theinvention is to providekan exchange of this character which isunattended, that is, one which does not require the constant attentionof a switchman. An unattended exchange may be left 'alone frequently forquite long intervals, and therefore special attention hasto be paid tothe possibility of certain troubles arising which might put part or allof the apparatus out of commission unless they were specially providedagainst.

IThere are numerous other objects and special features of the invention,all of which will be more fully pointed' out in the detailedspecification which is to follow, reference being had tothe accompanyingdrawings. i

Referring to the drawings, Figs, 1, 2, 3, and 4, when laid outinrectangular formation, with the corresponding lines at the edges ofthe several sheets in alignment, show suilcient of the apparatus andcircuits thereof to enable the invention to be explained and understood.Fig. 5, on the 1933, Serial No. 654:,93'1y same sheet with Fig. 3, is atrunk circuit which may extend to a, manual exchange. I Consideringsomewhat more in detail the yarious `items of equipment which are shownin the drawings, Fig. 1 shows two subscribers lines and the associatedline circuits `at the exchange. The line associated with line circuit #iis a full' metallic common battery party line. The'line may haveqas manyas forty stations, divided' code ringing being used. As is well known,this means that the subscribers are signalled by means ci.' code rings,part of the ringers being connected from one side 'fof the line toground, whiie the ringers at the other stations are connected from theother side of the iine to ground. The line associated with line circuit#2 is a grounded locai battery party line, and may have as many asvtwenty stations. The subscribers are signalled by means of code ringing.Line circuitv #il is similar to line circuit #iL it will be understoodthatwarious other types of lines may be con-u nected to the C.' A. X.,such as individual lines and party lines with bridged ringers. Suchlines are well known in the art and-hence have not been shown in thedrawings, but will be referred 25 to more particularly later on indiscussing the operation of the'system.

Connections between the various subscribers lines in the system andconnections from a subia scribers line to an outgoing trunk areestablished by means of a number of finder connector linksn One of theselinks shown in Figs. t and 2 of the drawings. It comprises a finderswitch, Fig. l, which is indicated by the appropriate label, and aconnector switch, Fig. 2, which is indicates. by the label connector.The iinder switch, Fig.. l, is preferably a rotary E-point switch, whitethe connector switch, Fig. 2, is preferably a 10h* l i line Strowgerswitch 4of the vertical and rotary type. Other types of switch, however,may of w course be used. The link circuit also comprises a number ofrelays which are lshown in Figs. i and 2, and a repeating coil which isshown in Fig. 2. It should bementioned also that the connectorhasassociated with it a small lll-point rotary switch CS which functionsas a code selector for ringing purposes.-

Common to all ofthe link circuits thereI is provided afinderdistributor, which is shown in 50 Fig. 3 of the drawings. Thisfinder distributor comprises a ten-point rotary switch having fourwipers and a number of relays for controlling the operation of thedistributor switch and also for controlling the operation of the findersof the common to the finder connector links. Fig. 4`

also shows an interrupter I, consisting of a number of relays, a ringingmachine including the generator GEN, and a number of other relaysl whosefunctions will be pointed out hereinafter.

As mentioned hereinbefore, Fig. 5 shows a trunk circuit which may beused for connecting' the C. A. X. in question with a distant manualexchange. At the manual end the trunk circuit terminates in a jack J,which has'associfK ated therewith the usual call signal lamp. At theother end, the line conductors of the trunk circuit extend to andterminate'in a subscribers line'equipment which may be the same as oneof the line equipments shown in Fig. 1.

The operation of the system will now be de#- scribed, it being assumedfor this purpose that the subscriber at station A ongtheparty lineassociated with line circuit #I desires to call the subscriber atstation B on the line associated with line circuit #2. When thereceiver' is removed at station A, a bridge is closed across the lineconductors 2 and 3 in the usual manner, and it follows that a circuit iscompleted for the double wound line relay 6, whichnis bridged across theline in series with the battery. Line relay 6 operates, and atarmatureI3 it connects ground to the private normal conductor I1, whereby theline is made busy in the banks of the connector switches. At armature I2the line relay 6 connects the cut-off relay 5 to the third conductor 30of the line circuit. This operation marks the line as calling in thebanks of the finder switches, the other terminal of the cut-off relay 5being connected to battery. Fi-

nally, the line relayy Bpplaces yground on the,

starting conductor 50 at armature II.

As a result of the grounding of start wire 50,

-a circuit is completed for the start relay 201 of the nder distributor,Fig. 3, the circuit extending by way of conductor 50, armature 23|,winding of relay 201, armature 228, and winding of -the stepping magnet2I3, to battery. It should be n'oted at this time that relay ,2I0 is`normally energized. `This relayrmay be termed an all trunk busy relay.It is held up over common conductor 254 by ground at all idle linkcircuits in multiple, so that this ground is not removed to permit therelay to fall back until all of the link circuits become busy. As a`result of the closure of its circuit as pointed out above, relay 201energizes and at armature 220 closes a pre-energizing circuit for theline relay |00 of the connector. This circuit extends from armature 220by way of resistance 2I5, wiper 202, conductor 25|, armature 89,conductor 55, `contacts controlled by armature |24 of relay |04, Fig. 2,upper left hand winding of the repeating coil, contacts controlled byarmature |20, and winding of line relay |00 to battery. The line relay|00 energizes over the above circuit and brings about circuit operationsin the link circuit which result in the grounding of the release trunkconductor 51. These operations will be discussed more in detail lateron.

As a further result of the energization of the start relay 201 in thefinder distributor, a circuit `places groundon conductor 255, therebyclosing a circiut through the lower winding of the stepping relay 205.'Ihe said relay thereupon operates and breaks the circuit of the'stepping magnet 54 at armature 2I4. Magnet 54 thereupon deenergizes, asa result of which the wipers of the finder -are advanced one step. :Thecircuit of the stepping Vrelay 205 is broken at the same time and thisrelay accordingly falls back and v again closes the circiut of thestepping magnet 54. The magnet and stepping relay, accordingly, continueto interact in this way and the finderswitch wipers are driven around inthe usual step by step manner in search of the calling line.

When the test wiper 52 reaches the marked test contact in its bank, thetest circuit is completed overa path which extends from ground at arma--ture 2I8, upper winding of the stepping relay 205, wiper 204, conductor253, the .lower winding of test relay 60, wiper 52, conductor 30,armature |2, armature 1, and winding of the cut-ofi.' relay 5, tobattery. The closure of the above circuit holds relay 205 energized, soas to prevent further rotation of the finder switch, and also energizesthe test relay 60 sufficiently to close its contact at armature 68. Itis immaterial whether the cut-off relay 5 pulls up upon the initialclosure of the circuit or not. When relay 60 closes contact 68, therelay thereby becomes locked to the grounded release trunk conductor 51.At the same time, the connection of ground to the test circuit at thispoint insures the full operation of the cut-off relay 5 of thesubscribers line circuit. The operation of the cut-off relay 5disconnects the line relay 6 from in bridge of the line at armatures I4and I0. The cut-off relay locks` itself to the conductor 30 at armature9 so that.

energizes although its operation is of no particular effect at thistime. Ground is removed from the start conductor 50 by the falling backof the line relay 6, or by the operation of relay 4.

Returning now to the test relay 60 of the finder,

a holding circuit including the upper winding is obviously completed toconductor 51. At armatures '61 and 10, the two sides of the subscribersline are extended by way of the line wipers' 5l' and 53, and the saidarmatures'61 and 10 to the talking conductors 55 and 56 o`f the linkcircuit. Conductor 56 is grounded yat armature |66 of the connectorcut-in' relay III. previously explained, extends to battery by w'ay ofthe winding of the line relay |00. A circuitfor the line relay |00 istherefore now completed over the calling subscribers loop.

In addition to the foregoing, the test relay 60 connects ground to theconductor 250 at its armature 69. As a result of this operation aeircuit is completed by way of conductor 250, wiper 20| of the finderdistributor, armature 2 I 6, and winding of the stepping magnet 2 I3, tobattery. Step ping magnet 2I3, therefore, energizes, and at theinterrupter contact of the magnet the circuit of Conductor 55, as

amature 220 is removed from the pre-energized circuit of the line relayin the link circuit. Ground is maintained on this circuit, however, fora short time longer by means of armature 2|1 of the slow-acting relay206 in order to insure that the calling subscribers line will beconnected through to` hold the line relay up as has been described inthe foregoing. 'Ihe falling-back of the start relay 201 also opens thecircuit of the slow-acting relay 206, which upon falling backdisconnects ground from the upper winding of the stepping relay 205. Itwill be understood that the latter relay was shunted by the connectionof grounded release trunk conductor 51 to the rtest circuit at armature68 of the test relay 60.l This renders relay 205 slightly slow to fallback so that it does not deenergize to close the stepping circuit atarmature 214 until the start relay 201 has deenergized. 'Ihe fallingback of slowacting relay 206 also breaks the circuit of the steppingmagnet 2|3 of the finder distributor at amature 2|6. This magnettherefore deenergizes and the wipers 20| to 204, inclusive, are advancedone step so that the distributor is associated with the nextlinkcircuit. The start relay 201 having deenergized, a test circuit isnow completed which extends from the test wiper 20| by {way o f armature2|9, armature 228, interrupter contacts of the stepping magnet 2|3, andthe winding of the said magnet to battery. If the next link circuit isbusy the contact engaged by wiper 20| will have ground on it and themagnet 2|3 will be momentarily operated to advance the wipers to thenext link circuit, this operation continuing until an idle link circuitis found.

In further explanation of the wayin which the link circuits are madebusy, in connection with conductor 250 of the link circuit shown inFigs.

v l and 2, it will be noted that this conductor is grounded whenever thetest relay 60 is energized.

After the connector has been operated and if the test relay 60 shouldfall back, as upon re- `lease of the connection, conductor 250 ismaintained grounded by way of the vertical off-normal springs VNI. Thusconductor 250 is maintained grounded continuously from the seizureof thecalling line until the link circuit is finally restored to normal byrestoration of the connector. It should be stated also that the linkcircuit can be made artificially busy by `operation ofthe busy key BK.

Attention will now be directed to the circuits of the link, Figs.' l and2, for the purpose of explaining more in detail the operations whichensue as a result of the energization of the linerelay |00. Uponenergizing, relay |00 completes a circuit for the lock-pulse relay 64over the following path: from groundat armature .235 of relay 2| I,

Fig. 3, by way of conductor 251, normally closed contacts-controlled byarmature |22 of relay |03, Fig. 2, armature |21 of relay |04, armature83 of j relay 66 and its back contact, armature |4 of the v line relay00, and winding of relay 64, to battery. Conductor 251 may be termed thesupervisory ground conductor and supplies ground to numerous operatingcircuits of the link for a considerable portion of theAtime of itsoperation.

For convenience this conductor and a number of ramications thereof havebeen shown by means of alternate heavy and light lines, so as to avoidthe necessity of tracing numerous circuits back to ground at armature235 of relay` 2H. By illustrating this supervisory ground conductor andits branches in this manner, supervisory ground can be picked up atnumerous points in 64 also opens the impulsing circuit at armature.

11, and at armature 15 supervisory ground is extended to the slow-actingrelease relay 65. Relay 65 thereupon pulls up and connects supervisoryground to the release trunk conductor 51. Conductor 51 is` thusgrounded, as brieiiy mentioned before, in order to hold up the testrelay60 and energize the cut-off relay 5 of the calling line. As a furtherresult ofthe grounding of the release trunk conductor 51, a circuit iscompleted from said grounded conductor by way of contact |42 of relay|01 in parallel with contact 9| of relay 6|, and thence by way ofarmature |26 of relay |04 and the winding of relay 66 to battery. Amongother things, relay 66 extends supervisory ground by way of its armature83 to the armature |'|5 of relay |00. This operation places theslowacting release relay 65under the joint control of the line relay |08and the lock-pulse relay 64. A further result ofthe grounding ofreleasetrunk conductor 51 is the completing of a circuit which extendsfrom said conductor 51 by way `of the vertical ol normal springs VN3 andthe upper winding of slow-acting relay |06. Relay |06 energizes, and atarmature |39 the impulse circuit is extended from the back contact ofarmature 11 of the lock-pulse relay 64 to the vertical magnet |80,preparatory to the receipt of impulses from the calling line. Relay |06also operates its armaturei 38 and thereby connects dial tone to theupper talking conductor of the link in order to notify the callingsubscriber that he can dial the called number.

The number of station B is 215. The rst two digits, the digits 2 and 1,are determined by the fact that the line of station B is connected inthe connector banks at the first set of contacts in the second level.This is clearly shown in the drawings. The third digit of the numberdepends on the code assigned to the desired substation B, and in thisinstance is arbitrarily assumed to be the digit 5.

pulse springs of the calling device in the usual and well known manner.At the first interruption the line relay 00, Fig. 2, deenergizes and atarmature` 4 breaks the circuit of the lock-pulse relay 64. Relay 64accordingly falls back and at armature 16 breaks its own lockingcircuit, so that when the line relay |00 is energized at the end of thefirst interruption the lock-pulse relay 64 will not pull up againforthwith. Lock-pulse relay 64 upon falling back also connectssupervisory ground to the impulse circuit which extends by Way ofarmature 11, armature 36, armature |30 and its front contact, andwinding of the vertical magnet |80, to battery. The vertical magnet |80accordingly energizes and steps the switch shaft carrying the wipers |82to |85, inclusive, up one step. The vertical magnet also closes acircuit for relay 64 which extends from ground, contact of verticalmagnet, armature ||4 of line relay |00, (which may be energized again bythis time).

and winding of relayv 64 to battery. Relay 64 therefore again energizes,locks itself at armaturev 16, and breaks the vertical magnet circuit atarvopposite the second level of bank contacts.

mature 11. The vertical magnet now falls backv preparatory to takinganother step.- On the next interruption received from the dial, the linerelay |00 and the lock-pulse relay 84 operate as before and the resultis that another impulse is transmitted to the vertical magnet |80,thereby stepping the switch shaft up so that the wipers stand At the endofthe series of impulses relays |00 and 64 come to rest in energizedposition.

During the transmission of the series of impulses as just described, therelease relay is controlled jointly by the line relay and the lock-pulserelay 64. Relay is slow acting and has to be maintained operatedthroughout the series of impulses. Since the operating times of relays|00 and 64 overlap to a certain extent, the maintaining of relay 64 inenergized position is more certainly assured than if the relay werecontrolled by the line relay alone.

At the first upward movement of the connector switch shaft, the verticaloff normal springs are shifted in the usual manner. The vertical offnormal springs VN1 have already been referred to. The off normal springsVN2 prepare a circuit for the release magnet |86, which, however, isopen at this time at armature 86 of relay 66. The off normal springs VN3break the circuit of the slow-acting relay |06. This relay, however, ismaintained energized in parallel with the vertical magnet |80 during thefirst series of impulses. At the end of the first series of impulsesrelay |06 falls back and at armature |89,the impulsing circuit istransferred to the rotary magnet |8|.

The calling subscriber may now dial the second digit l of the callednumber. This operation produces a single interruption in the subscribersloop and causes the line relay |00 to deenergize momentarily a singletime. As described in the foregoing, the lock-pulse relay 64 iscontrolled by the line relay |00 and transmits an impulse this time tothe rotary magnet |8|. The rotary magnet operates responsive to thisimpulse and steps the switch shaft around one step so that the wipers ofthe switch move in on to the first set of contacts in the second level.

During the transmission of impulses to the rotary magnet, theslow-acting relay |08 is energized in parallel with the magnet and atarmature |49 it completes a circuit which extends from said armature byway of armature |44, armature |64, the winding of relay |09, to battery.Relays |08 and |09 are both slow-acting relays and they remain energizedduring the rotary operation of the switch. It should be noted at thistime that in its energized position relay |09 extends ground from therelease trunk conductor 51 by way of armature |52, to the contactsprings of the rol tary magnet |8|. These contact springs have thefunction of re-operating the lock-pulse relay 64, as described inconnection with the vertical magnet |80. The circuit described isemployed rather than a circuit extending direct to ground so as toinsure that the relays |08 and |09 will become fully energized beforethe iirst pulse is terminated.

At the end of the rotary movement of the switch, relay |08 falls back,and breaks the energizing circuit for relay |09. This latter relay, whenit first energized, prepared a circuit at armature |54 for operatingrelay |02. Accordingly when ground is removed from the circuit of relay|09, relays |02 and |09 are energized in series over a circuit whichextends from ground at the busy key by way of armature 64 of relay 60and vertical olf normal springs VNI. Winding of relay afiliarseY |92,armature H8, contactav controlled byarmature ||1, armature |54, andwinding of relay |99. to battery. Upon energizing over the abovecircuit. relay |92 locks itself at amature ||1 independent of relay |99.Belag energizes. 'Ihe operation an locking up of relay |02 is effectiveat this time to transfer the impulse circuit at amature ||9 from therotary magnet |8| of the connector switch to the stepping magnet |92 ofthe code selector CS.

'Ihe connector has now been set on the desired called line, but the linehas not been tested as yet. 'I'his operation is deferred until the codeselecting digit is dialled. When the calling subscriber dials the lastdigit 5 of the number, five interruptions are produced in the loopcircuit and relays |00 and 64 respond in the manner already described totransmit live impulses to the stepping magnet |92. As a result thewipers and |9| are advanced ilve steps so that they come to rest on theflf th contacts of their respective banks. Relay |08 is energized inparallel with stepping' magnet |92 and at armature |49 closes a circuitfor the slow-acting relay |09. These two relays accordingly aremaintained in operated position throughout the series of impulsestransmitted to the stepping magnet |92. On the first step of the codeselecting switch CS, the rotary ou normal springs RN are closed, and acircuit is completed for relay ||8. There is a resistance in thiscircuit and relay I8 only operates part way, sumcient to shift itsarmatures |18and |11. Armature |16, however, is not operated at thistime. At armature |11, the release circuit is transferred from releasemagnet |86 of the connector switch to release magnet |98 of the codeselector. At armature |18 the test wiper |88 of the connector isconnected up.

Since relays |08and |09 are operated during the rotation of the codeselector CS, a circuit for the test relay |05 is prepared at armature|58 of relay |09. 'I'his circuit is completed at armature |48 of relay|08 when this relay falls back at the end of the series of impulses tostepping magnet |92. The operation now depends on whether the calledline is busy or idle. If the called line is busy there will be a groundpotential on the test contact engaged by wiper |88 and the test relay|05 will pull up over a circuit which extendssfrom the grounded testcontact by way of test wiper |88, armature |18, armature |58 and frontcontact (slow-acting relay |09 is still energized), armature |48, thewinding of relay |05, to battery. Relay |05 accordingly` energizes andprepares a locking circuit for itself at armature |82. The slow-actingrelay |09 deenergizes now and the locking circuit is completed from thegrounded conductor 51 by Way of the armature |32, contacts controlled byarmature |58, armature |48, and winding of relay |05 to battery. As afurther result of its operation relay |05 opens the circuit of thecut-in relay at armature |85, and at armature |86 the impulse circuit istransferred on to the conductor which leads to armature ||4 of the linerelay. The latter precaution is necessary in order to provide a circuitfor re-operating the lock-pulse relay 64 'in the event that the callingparty should happen to dial a digit or accidentally open his linecircuit momentarily while connected to a busy line.l Were it not forthis provision the lock-pulse relay 64 would fall back and could notagain become oper ated because there is no stepping magnet beingcontrolled at this time. If permitted to remain 5 ground the privatenormal conductor of the busy line and would prevent such line fromdisconnect,-

ing. The arrangement described insures' that when the lock-pulse relay64 falls back responsive to a momentary interruption of the line it willimmediately close a fresh circuit for itself by way of armature |36 ofthe test relay |05 and armature IH of the line relay |00. 1

further result of the operation of the test relay 05 is the placing of abusy tone on the talking circuit at armature |30. This noties thecalling subscriber that the desired line is busy and he will accordinglyhang up his receiver. Upon the replacement of the receiver the linerelay is.deenergized, followed by the falling back of relay 64. ,Sincerelay vl|00 remains back. relay 64 cannot close an energizingcircuit-for itself and both these relays remain deenergized. 'I'herelease relay 65 therefore falls'back and removes ground on the releasetrunk conductor 51.

, also deenergizes the cut-off relay of the calling line.

The removal of ground from the release trunk conductor 51 also permitsrelay 66 to fall back and close the release circuit which now extends tothe release magnet |93 of the code selector. The code selector CS isthereupon restored to normal and upon reaching normal position theoir-normal springs RN are opened.

This causes relay I|3 to fall back and transfer the release circuit tothe release/ magnet |86 of `the connector. The connector is thereuponrestored in the usual manner. Test relay |05 is, of course, restoredwhen ground lis removed from the release trunk conductor 51.

It will be assumed now that the called line was found idle. Under thiscondition, there will be no ground on the test contact engaged by thetest wiper |03, and when the circuit of the test relay |05 is completedby the deenergization of relay |08 said test relay will not pull up.Shortly after relay |08 falls back, relay |09 falls back, and a circuitis completed for thev cut-in relay `This circuit may be traced from `thesupervisory ground conductor by way oi?l armature 00 of the releaserelay 65, armature |35, upper winding of cut-in relay armature |53,armature |18, test wiper |03, test contactengaged thereby, conductor 26,upper armature of the line relay 24 of the called line, Fig. 1, andwinding of the cut-off relay 23 to battery. Upon the closureof` thiscircuit the cut-in relay I and the cut-oil? relay 23 of the called lineare energized in series. The cut-off relay 23, upon operating,disconnects the line relay 24 from the called line. The cut-in relay nupon energizing, connects up the line wipers |82 and |05 at armatures|58 and |68, respectively. At armature |61 the impulse circuit to themagnet |92 is opened. At armature |65 supervisory ground is connected tothe test wiper |83, .thereby short circuiting the upper winding of relayRelay III. however, locks itself energized at armature |6|, by means ofwhich a circuit for the lower winding of relay is completed to ground atarmature 0I of relay 66. Relay also, breaks the circuit of relay |09 atarmature |64, and at armature |63 it prepares a circuit for the pick-uprelay ||,2. A circuit for th"l ringing relay |0 is also prepared atarmature |62, likewise a circuit for relay |10 at armature |59.

The connector is now ready` to ring the called subscriber. When thecut-in" relay pulls up it grounds the start conductor 301 for startingthe ringing equipment shown lin Fig. 4.. The detailed operation ofv thisequipment will not be gone into at this time.- Fory the purposes of thepresent description, it lwill be suiiicient to state that ringingcurrent is supplied over conductor 300, while intermitent groundimpulses in code are transmitted over conductors such as 33|, 332, etc.,to the banks of the code selector CS. It the ringing equipment is innormal position when the cut-in relay pulls up, a circuit is immediatelycompleted over the pick-up conductor' 306 for the pick-up' relay |I2. Ifthe ringing equipment is not in normal position, this circuit iscompleted by wiper 305 of the code switch CCS when it reaches the firstcontact in its bank, at the beginning of a code cycle.

Upon energizing, the pick-up relay ||2 locks itself to ground'atarmature |14. In addition relay ||2 grounds the lower line wiper |85 atarmature |15. The purpose of 'this is to complete a return path forringing current in case the line about to the signalled has fullmetallic ringing. Finally, relay ||2 completes a circuit for theiringingrelay ||0 at armature |13. Wiper |9| is standing on the fifth contact inits associated bank, so that now a cofde comprising two spaced groundimpulses is transmitted from conductor 330 by way of the fifth contactin the vbank oi' wiper |9|, the said wiper |9|, armature |16, armature|13,l upper winding oi ringing relay H0, armature |62,`interruptercontact of the rotary magnet I8 I, and lower winding of ringing relay||0 to battery. The ringing relay ||0 is thereby operated in accordancewith the code |-|.I l

Each time the ringing relay operates it closes a circuit at armature |55whereby ringing current from the conductor 300 is transmitted tov thewiper |82 of the connector and thence by way of conductor 25 to the lineconductor 20 of of the called line, Fig. l. Fromline conductor the'ringing current flows through all the ringers on the line in parallelto ground. The ringers are all actuated therefore in accordance with thecode I-I, and since this is the code assigned to station B thesubscriber at that station is notified to answer his telephone. Eachtime that relay ||0 pulls up it/also closes a circuit for relay |10. At.its left hand armature,| 69 relay |10 connects ringing current by wayof the small condenser to the upper conductor of the talking circuit soas to transmit a ringing tone to the calling subscriber. This informsthe calling subscriber that the called line is being signalled. Relay|10 also connects a shunt around relay 63 at its right hand armature|12, and this. shunt is maintained for a short interval after theringing relay ||0-.falls back, relay |10 being slightly slow acting. Thepurpose of this shunt is to provide a non-inductive path for dischargingthe condensers on the line each time :the ringing relay ||0deenergizes,`

so as ,to eliminate any chance of falsely operating relay 63.

When the called subscriber at station B removes his receiver to answerthe telephone, a conductive circuit is completed fromground by way ofthe secondary winding of the induction coil and the receiver to the lineconductor 20. At the rst silent interval this results in the completionof a circuit forA relay 63 which extends `by way of the conductor 20,normal conductor`25, wiper |83, armature |58, armature |55 (ringingrelay ||0 being deenergized) upper right hand winding oftherepeating-coil, ar-

mature 14, and the winding of relay 63 -to battery. Uponenergizing-relay 63 closes at its armature 13 a circuit for relay |03.Upon energizing, relay |03 at its armature "|I9' closes a circuit forthe ring cut-off relay 01. Upon energizing, the ring cut-off relay |01locks itself at armature |4|. At armature |40, relay |01 closes Y thetalking circuit by completing the connection between the two right handwindings of the repeating coil. At armature |43, relay |01 breaks thecircuit of the pick-up relay ||2, which thereupon falls back 4and breaksthe circuit of the ringing relay at armature |13. At armature |44 `relay|01 breaks the circuit of relay |09 and also prepares' a circuit for thelock-pulse relay 64. This latter circuit is effective to reenergize thelock-pulse relay in the event that the calling subscriber should dial anadditional digit or in some -way accidentally open his line circuitmomentarily. At armature |46 relay, |01 disconnects ground from thestart conductor 301, so

that the ringing equipment will be brought to calling line. In furtherexplanation of this operation, it should be pointed out that when thecutin relay III of the connector operates (as previously described) itdisconnects ground at armature |66 from the lowerv line conductor 56 andthereby removes the short circuit from the winding of relay I 0|. Thisrelay accordingly energizes over the calling line in series with relay|00. Upon energizing, relay |0| breaks the circuit of'relay |02 atarmature ||6. Relay |02 thereupon deenergiz'es. Since relay |02 isdeenergized, the operation of relay 03 will reverse the current in thecalling line, as stated. However if a grounded line, such as the linehaving the substation B, had been calling, the lower line conductor 56would have remained grounded at the line circuit so that the removal ofground at armature |66 of the cut-in relay would have had no eifect.Relay |0| would therefore have remained short circuited, relay |02 wouldhave remained energized, and the operation of relay 03, therefore, wouldhave been ineffective. The arrangement including relay |02, therefore,provides for discriminating between metallic circuit lines and groundedlines, the relay |03 being ef fective to reverse the connections of therelays |00 and |0| to metallic lines, but being ineiective to reversesuch connections in the case of a grounded line. The reversal is of noutility in the connection which has just been described, that is, whenthe line to which substation A is connected is the calling line. This isa standard operation, however, and is of utility, for example, in thecase'of acalling line which is equipped with a pay-station. The systemillustrated may well include several pay-station lines and theyprovisions for reversing the current are therefore essential. It isalso required on calls over trunk lilies such as the one disclosed inFig-`l 5, as will be mentioned later on.

The required connection has now been completed. The calling line issupplied with talking current through the windings of the relays |06 and|0| and the left hand windings of the repeating coil. 'I'he called lineis a local battery line and station B therefore is not supplied withtalking current from the connector. A talking circuit. is, however,completed from ground at the line equipment by way of normal conductor28,' wiper |85, the two right hand windings of the repeating coil inseries, and wiper |82 to the line conductor 20 by way of normalconductor 25. The talking circuit has been drawn in by means of heavylines and will therefore be readily.traced. I y

When the called subscriber hangs up his receiver relays 63 and |03 aredeenergized. When the calling subscriber hangs up his receiver relays|00 and |0| are deenergized. Relay |00 .breaks the circuit of relay 64,and the release relay 65 accordingly falls back after a short interval.The connection is thereupon released in substantially the same manner ashas been previously descr 'bed in the case of release from a busy line.

The operation of the apparatus shown in Fig. 4 will now be described indetail, without reference to any particular call. 'I'he start conductor301 is common to all the link circuits, that is, it extends to contactson the cut-in relays such as relay of all the connectors. When anyconnector establishes connection with .a called line and the cut-inrelay, such as loperates, ground is connected to the start conductor301. As a result a. circuit is completed for the relay 3|5. Relay 3|5closes a circuit for the motor of the motor generator set at itsarmature 320.

machine in operation with the result that ringing currentis generatedand projected out over conductor 308. This conductor extends to all ofthe connectors for the purpose of supplying ringing current. i

The operation of armature 320 of relay 3 5 also extends ground to therelay interrupter comprising relays 3| 3|2, and 3|3. Relay 3|| thereforeenergizes and removes a shunt circuit from relay 3|2, which thenenergizes also. Relay 3|2 then removes the shunt circuit from relay 3|3,so as to permit it to energize. The latter relay short circuits relay 3|I and causes it to fall back, whereupon relays 3|2 and 3|3 aresuccessively short circuited and deenergized. The latter relay thenremoves the short circuit from relay 3| and permits it to pull up again.These operations continue as long as ground is supplied, with the resultthat impulses are transmitted over conductors 330 and 329. Conductor 330is connected in multiple to wipers 30| to 304, inclusive, of the codingswitch CCS, while conductor 329 extends to the stepping magnet 309 ofthe coding switch.

`The magnet 309 is therefore intermittently operated to advance thewipers 30| to 305, inclusive, step by step over their associated banks.The operation of the coding switch in producing various codes of groundimpulses on the code ringing conductors will rst be described.

Considering' wiper 30| it will be observed that the fifth andseventhcontacts of its bank are connected to master code conductor 34|.As the switch is advanced step by step over its bank con tacts wiper 30|will eventually rest for a moment on the fth bank contact. When the nextimpulse is delivered to conductor 330 this bank contact accordinglybecomes grounded and a ground impulse is transmitted to master codeconductor conductor permitting the switch to advance its wipers to thenext set of contacts. 'Ihe operation thus continues, and when wiper 30|rests on the seventh contact in its bank another ground impulse isdelivered to the master code conductor 34|. It will be seen, therefore,that in one complete cycle of operation of the code' switch two spacedground impulses will be delivered to the master code conductor 34|.

In the case of wiper 302, it will be clearly seen on inspection thatthis'wiper during the same cycle of operations will deliver two groundimpulses to the master code conductor 342 from the fourth and fthcontacts of its bank and two aditional ground impulses from the seventhand eighth contacts. Also it will be seen that wiper 203 will deliverthree ground impulses so master code conductor 343 from the third,fourth, and fifth contacts of its bank, followed by three more groundimpulses from the seventh, eighth, and ninth contacts in its bank. Wiper304 is the 4-4 code wiper and delivers in an obvious manner four groundimpulses to master code conductor 344 followed by four more groundimpulses.

Fromthe foregoing it will be understood readily `enough that the coderinging conductor 335,

L338 are directly connected to the master code conductors 343, 342, and34|, respectively.

In order to produce the combination codes in which the number of ringsin the two halves nf v the code are unequal, the re1ays'3l8 and 3|9 areemployed. Relay 3| 3 is energized over wiper 30| in the rst positon ofthe code switch CCS. This relay locks to the grounded-start conductor301. When wiper 30| of the coding switch CCS arrives at the sixthcontact in its bank a circuit is completed for relay 3| 8. This relayoperates and breaks the locking circuit of relay 3|9. The latter relayaccordingly falls back and a locking circuit is closed for relay 3|3.When wiper 30| again arrives at the first contact of its bank relay 3|3is again energized and relay 3|8 is unlocked. Relay 3|3 is thereforeenergized while the Wipers of the coding switch are traversing thecontacts in the rst half ofthe bank, while relay 3| 8 is energized whilethe wipers are traversing the contacts in thesecond half'of the bank.

From the foregoing it will be easy to deduce the codes which aretransmitted over the remaining code ringing conductors. In the case ofcon ductors 33|, for instance, the code transmitted over this conductorconsists of four short rings follower by three short rings. During thefirst half of the code switch cycle the conductor 33| is connected byrelay 3|9 to master code conductor 344, from which it receives fourground impulses, while during the second half of the, cycle the codeswitch conductor 33| is connected by relay 3| 8 tol master codeconductor 343 from which it receives three ground impulses. Thus thecode transmitted over the ringing conductor 34| is 4-3.

In the same way it will be seen that code ringingconductor 332 receivesva code consisting of four impulses followed by two impulses. By way offurther example, conductor 333 receivesthree impulses followed'by fourimpulses, while'conductor-334 receives four impulses followed by twoimpulses. It will be'unnecessary to consider in ydetail the remainingcode ringing conductors asA the ground impulse combinations transmittedover them will be apparent 'from the drawings.

It remains to consider the special direct line ringing conductor 333,which is provided for ringing individual lines and any other situationswhere a single long ring is desired. This conductor extends tocontactspf relay 3|9 so that during the first half of the cycle ofoperation of the coding switch CCS it is connected down to a contact onrelay 3| 0. The relay 3m is energized continuously while grounded wiper305 is in engagement'with the second, third, and fourth contacts of itsbank. Thus, by the operation of relay 3|0 a relatively long applicationof ground is made to conductor 333. y

Wiper .305 also controls the application of ground to the pick-upconductor 306. If the coding switch CCS is in its normal position theconductor 306 is grounded, so that when a connector is cut in on acalled line the pick-up relay, such as relay I2, is energizedimmediately. However, if the code switch should already be in operationdue to the fact that a subscriber is being signalled from anotherconnector switch, the energization of the pick-up relay will have toawait the grounding `of conductor 306 by wiper 305 when the codingswitch arrives at its rst position. The use of the pick-up conductor iswell understood, its function being to insure that a mutilated code willnot be applied to a called line, as would happen if a connector werepermitted to start ringing with the coding switch in any randomposition.

The operation. oi?` the relays ^associated with the relay 3|5 will nowbe more particularly described. When relay 3|5 is energized it closes acircuit for a signal lamp in series with an alarm relay 330. At the sametime a circuit is prepared relay energizes, locking itself to thegrounded start conductor 307. Relay 3|1 opens the circuit of relay 3|6at armature 323, and at armature 321 it breaks the circuit of the .alarmrelay 330. Relay 3|6 on falling back, breaks the circuit of relay 3|4`,`which accordingly deenergizes also. As a result relay 3H remainsenergized until the ground is removed from start conductor 301.

The purpose of the foregoing operation is to test thestarting of thecoding switch CCS and the ringing machine. It will be obvious that ii?4the coding switch failed to start the described operations could not becompleted,l nor could they be completed if the. ringing machine failedto produce ringing current.4 The circuit of the alarm relay 330 wouldtherefore remain closed and an alarm would be transmitted to thedisftant exchange where the wire-chief, or other official charged withthe duty of maintaining the equipment in operation, has his station. The

circuits by which thealarm is transmitted form no part of 'thisinvention and hence have not been shown. v

When ground is removed froml conductor 301,

relays `@H5 and 3II fall back. Relay 3I5 stops 'the ringing machine andthe interrupter I by removing ground at armature 320. Relay 3I5 alsocloses a circuit at armature 32| for restoring the coding switch CCS tonormal. These contacts close a self interrupted circuit for the steppingmagnet 309 in an obvious manner, which is broken by wiper 305 when theswitch reaches normal.

In the foregoing description the dialling circuit in the connector hasbeen only briey described, as it was considered that -it would beinconvenient to interrupt the explanation in order to discuss it indetail. Some further consideration will therefore be given to thedialling arrangements in order to point out their advantages somewhatmore fully. It has already been stated that the system herein shown anddescribed is intended for use in a small community where as a rulevarious types of lines will be found in use. The dialling conditionsaccordingly will vary between wide limits. Someof the lines may` not bevery well insulated and there will be on such lines, therefore, aconsiderable leak" to ground. The bridged ringers on the party lines,whether bridged across the line or to ground, impose a condition on theline relay which is somewhat similar to that imposed by a leaky line.The line relay will tend to fall back slowly and to energize quickly,with the result that very short impulses will be produced at its backcontact during a series of dialling impulses. There may be other'linesin the system which are relatively long and of high resistance, and ifthe insulation on these lines is good an entirely different conditionwill be imposed on the line relay. When dialling impulses from'such aline are being received the line relay will tend to fall back quicklyand pull up slowly, resulting tin long impulses at its back contact andvery short impulses at its front contact.` The improved diallingcircuits which are herein shown and described meet these conditions witha maximum of efficiency. The tests have shown that satisfactory diallingcan take place with these circuits overv a line which has'a leak toground' which is as low as 3500 ohms, and such line may at the same timehave as many as twenty stations on it with their ringers either bridgedacross the line or bridged from the same side of Vthe line to ground.The same connector as used in the foregoing will also operatesatisfactorily on a long line having substantially no leak to ground andas high a resistance in the loop as 1200 ohms.

vThe arrangement by which these results are accomplished will be pointedout somewhat more in particular.

To begin with, the line `relay is given a very stir; adjustment, thatis, the Contact springs which correspond to armatures I I4 and I I5 areadjusted very stiiiiy so that the relay will be sure to fall back eachtime that its circuit is interrupted even though dialling is takingplace over a line which has the maximum leak to ground. It should bestated, however, that the adjustment is made only stiif enough to insurethat each time the line relay circuit is interrupted the contact will bebroken at armature III. The special lock-pulse scheme which is includedmakes it immaterial whether armature II5 makes on its back contact ornot. The lock-pulse arrangement includes a relay 64, which is droppedback every time the line relay |00 opens its contact H4. Relaylondropping back opens its own locking circuit and closes the circuit forthe stepping magnet such as |00. This insures that the stepping magnetwill be energized fully each time relay 64 drops back, because thelatter relay cannot pull up again until they stepping magnet operatesfully. These circuits have been gone over before, and hence it will beunnecessary to trace them in detail.

The lock-pulse arrangement for securing a more positive delivery ofimpulses to a stepping magnet by a line relay is not broadly new.- vInone such arrangement which is well known, the line relay deliversimpulses to the stepping magnet at itsbackcon'tact. In parallel with thestepping magnet is a quick acting lock-pulse relay which pulls up at thebeginning of the impulses and connects a locking ground to the impulseconductor so that the relay is maintained energized and the fulloperation of the magnet is insured. The magnet on completely operatingthen disconnects this ground so that it and the lock-pulse relay canfall back. This arrangement, it will be seen, depends on the quickenergization of a lockpulse relay, the theory being that a relay can bemade to energize more quickly than the stepping magnet. The presentarrangement, however, is much more Adesirable than the one described.The present arrangement depends on the falling back of a relay such as-64 upon the opening of contacts at the line relay. This arrangement hasan advantage for several reasons. In the rst place the time which isrequired for a relay to fall back is less than the time which isrequired for a relay to pull up. Consequently, a relay such as 64 willfall back quicker than the lock-pulse relay will pull up in the priorknown arrangement. In the second place, when a lock-pulse relay is usedlike relay 64, which falls back to transmit impulses to the steppingmagnet, it permits the control of the relay to be exercised over a frontor make contact on the line relay instead of at a back contact.`In`deenergizing, the line relay of course breaks its front contactbefore it closes its back contact, so that here again a considerableadvantage is presented. A close observation of the line relay I 00 whendialling is taking place over a very leaky line shows that the linerelay barely separates its front contact at armature I I4 with eachinterruption of the circuit and never closes the back contact atarmature I I5 at all.

As stated hereinbefore, an altogether different condition is imposed onthe line relay when dialling is taking place over a high resistanceline. Under these conditions, the line relay will tend to fall backquickly and will have difficulty in pulling up completely each time thecircuit is closed between interruptions. In order to assist the linerelay in operating under these conditions, a priming leak resistance 81is provided. When the line relay falls back a circuit is completed fromground by way of armature I I5 and its back contact, aramture 19,resistance 81, and the winding of the line relay |00 to battery. Thiscircuit is effective only under the conditions mentioned, that is, whenthe line relay fully deenergizes on each interruption of its circuit. Itprovides a circuit for partially energizing the line relay so that eachtime the loop circuit is closed at the calling device the relay canrespond with the necessary speed.

It will not be necessary to consider the operation of the system whencalls are made from other lines than the line of station A, except in avery general way. It will be clear that all of the full metallic linesin the system, whether individual '.single line conductor to groiind.

When the station B is calling for instance, the

- removal of the receiver grounds the line conduc' tor through the.telephone instrument and operates the line relay 2li.. `Thisstartsthender switch oi.' an idle link/circuit. in the usual way.

suming that th finder link circuity shown in .t `e drawings is used,when the finder locates the calling line the wiper 5| will makeconnection with the lineA conductor 20, while thel wiper 59 will makeconnection with the conductor 2 l This conductor in' the case of agrounded line is com nected to ground as shown in the drawings. When thesubscriber dials the line relay |00 is controlled over a groundedcircuit which does not dner materially from the circuit over which thisrelay was controlled in the case of a call initiated at the line ofsubstation Ai, In that case, it will s be recalled, the lower lineconductor 3 is connected. throught() 1mi; talking conductor se which 'isgrounded at the connector throughout the dialling operation. Inthe caseof thelinesof station B the circuit is grounded at the substation andconsequently the'dialling circuit will have a little less resistancethan in the other case. When the v connection is completed the talkingcircuit will extend overthe heavy talking conductors. It will beobserved that this talking circuit includes both of the left handwindings of the repeating coil in theusual manner,`the lower terminal ofthe lower winding being connected by way of talking circuit conductors56 and 2l to ground at the line circuit. Since the telephone instrumentat station B isconnected between the line conductor 2li and ground, acomplete path will exist over which conversation may be held.

It will be convenientnow to explain how a subscriber such as thesubscriber vat station A calls another subscribed on his own line. Thisis what is known asa revertive call. It will be assumed that the desiredstation is station C, the` number of which is i522.,

When the receiver is removed at station A the same operations take placeas have been heretofore described, with the result that the calling lineis picked up by the nder switch of a finder connector link. Assumingthat the link shown in the drawings is used, the finder switch will es-ytablish connection to the calling line as previously described andcircuits will be completed automatically for placing the connector underthe control of the calling dial. When the first digit 6 of the desirednumber is called the connectorl wipers are stepped up to the sixth levelin their respective banks. Following this the second digit 2 of thecalled number of dialled, with the result that the connector wipers arerotated two steps so that they come to rest on the second set of bankcontacts in the sixth'level. The subscriber now dials the last digit 2of the number, causing the code selector'CS to advance its wipers twosteps. Following the operation of the code selector switch CS, thecalled line is tested in the manner'hereinbefore described, and ofcourse it is yfound che busy. This, it wm be understood, isbecause thecalled line is also the calling line.'

Upon receiving the busy signal, the calling subl scriber hangs up hisreceiver. The subscribers on party lines have special instructions andsuch asubscriber knows that when he calls a party on his own line hecanexpect to get a busy signal and that lthe proper procedure in such acase is vto hang up his receiver` and wait a suiiicient` length of timefor the signalling operation 4to take place. I'

When the receiver is replaced at station A line relay |00 falls back,followed by the falling back 'of relay 64. Accordingly, the slow actingreleaserelay 65 is deenergized an instant later. Relay 65 ondeenergizing removes ground from the re ,lease trunk conductor 51 at itsarmature 18, but

prior to this a fresh ground has been connected up in a manner whichwill now be explained. When relay Et falls back it closes a circuitwhich extends from supervisory ground by way of armature 16, armature84, armature |34 ofthe busy relay |05, and thence to thetest wiper |83.The

test wiper is now in engagement with a test conf tact to which theprivate normal conductor |1'ls connected so that ground is thereforeextended by way of conductor i1, back contact of arma= ture l i3 of theline relay 6, Fig. l, armature 9 of the cut-od relay 5, conductor 3B,test wiper 52, and armature 60 to conductor 51 of the link circuit. Thusground is maintained on conductor 51 to hold relays 5,r 6 0, and 66energized so as to maintain the connection. i

When the release relay 65 falls back it `com pletes a circuit at theback contact of its armature 18 which extends from the groundedconductor 5l by way of armature 82 and armature |39 to the relay 6i,which thereupon energizes. Relay 'SI closes a locking circuit for itselfat armature 92, and opens the heavy talking conductors 55 and 56 atarmatures 89 and 93, respectively. In addition, relay 6| opens a pointin the circuit ,of relay 66 at armature 9| Relay B6 is, however, heldenergized for the time being by way of armature |42 of relay |01.Finally relay 6i closes a circuit at armature 90 lwhich extends throughthe lower winding of the cut-in relay to battery.

Relay i'i thereupon energizes and brings about i ing machine is startedupl and the proper ringing current is transmitted out over the calledline;V

This operation will be described in so far as is necessary in order topoint out the operation of the connector in shifting the wipers of thecode' selector CS. i

It will be recalledthat in thisinstance the Wipers of the connector havebeen raised to the sixth level. At the sixth level the shaft springs orlevel olf-normal springs LN3 are closed by a cam on the connector shaft.These springs operate only on the sixth level. With the springs LN3closed, the resistance in the circuit of relay ||3 is short circuited,so that when the code selector CS is stepped oi normal relay H3completely energizes, and operates its armature |16 aswell as itsarmatures |18 and |11. By the operation of armature |16 the upper wiper|90 of the code selector is substituted for the lower Wiper 9 'Ihepurpose of this arrangement will be readily understood. The codeselector CS is only a tenpoint switch and without some specialarrangement, therefore, it would only serve to select from ten diierentcodes. In the present system, however, it is assumed' that there will beat least a few large party lines which require twenty codes. These partylines are multipled in two diierent lev'els in the bank of th connector.The line of.

v,station A,- f'or instance, is not`only multipled in the third level ofthe connector banks, but it is also multipled in the sixth level. Theline is connected with just the same 'regardless "of which level iscalled,-but when the line is called by way of the third level wiper |9|of the code selector is used whereas if the line is called by way of thesixth level, wiper |90 of the code selector will be used. #This doublesthe capacity of the code selector and makes it possible to usev twentycodes.

While on this subject, it may be well to digress a little further andcall attention to the arrangement which is made for enabling as many asforty parties on a line to be signalled. The line of station A isconnected up as a forty-party line. As described in the above paragraphthe line is multipled in the first contact set of the third level andalso in the second contact set of the sixth level, which provides forsignalling twenty parties on the line. be selected by the code selectorCS and twenty parties corresponding to these codes may therefore beplaced on the line. These twenty parties all have their grounded ringersconnected to the upper line conductor 2. Normal conductor I6 isconnected to conductor 2 and at the other end is multipled to bankcontacts in the third level and the sixth level whichare engaged by theactive wiper |82 of the connector. Wiper |82 of the connector is thewiper over which ringing current is transmitted. Now, there may be.twenty additional stations connected with the line which have theirringers connected between line conductor 3 and ground. In order toenable these' twenty subscribers to be signalled two additional sets ofbank contacts. are assigned at the connector. As shown in the drawings,these additional sets of ybank contacts are the first set in the fourthlevel and the third set in the sixth level. The normal conductors IB'and|9 are connected up to these two additional set of bank contactsreversed. That is, normal conductor I9 which is connected to conductor 3at one end is connected at. the other end to contacts in the fifourthand sixth levels which are accessible to n wiper |83 so as to providefor transmitting ringing current over the lower line conductor 3 insteadof over the upper line conductor 2. It is assumed that ordinarily onelevel such as the sixth level, which is assigned for ringing those partylines which have a large number of subscribers, will be sufcient to takecare of all the lines of this character that there are. However,

if this is not the case, an additional level, such as the seventh level,could also be assigned for this purpose and' the level oil normalsprings LN3 would then be constructed so as to close on both the sixthand seventh levels.

Returning now to the point where the description was left off, when theringing equipment was started by the application of ground to conductor301, the code switch CCS transmits ground impulses over the several codeconductors as has been previously described. The code conductor 360 isthe one which is concerned in the present connection, as this is theconductor which is 'selected by wiper |90 of the code selector CS. Thecode conductor360 is the conductor for the 2-4 code. and accordingly itreceives two ground T hat is, twenty different codes may impulsesfollowed by four ground impulses.v -These impulsesy operate the ringingrelay I in the manner heretofore described and the relay transmitsringing current over wiper |82, normal conductor |6,and conductor 2 ofthe line inthe proper manner to signal the subscriber at station C. Itis assumed that Astation C is the station to which the code 2- -4 isassigned. It should be mentioned at this point that during thesignalling operation relay breaks, the circuit of the busy lead at theback contact of armature |69 each time ringing current is applied to thecalled line. 'Ihis is to prevent theringing current from backing up onthe busy lead, which may at this time be connected up in anotherconnector switch. This provision is only useful on a reverting call,since it is only on a call of this kind that the busy lead is connectedup during'theringing operation, this being due to the fact that in arevertive call the busy relay |05 is energized.

When the called subscriber at station C answers his telephone, theremoval of the receiver closes a circuit in the previously describedmanner for relay 63. This relay pulls up and closes a circuit for relay|03. 'The latter relay on energizing -closes a circuit for relay |01,all as previously described. Relay |01 upon energizing opens the circuitof relay 66 at armature |42. called that'it was previously pointed outthat the energization of relay 6| opened one point in' the circuit ofrelay 66. On relay |01 operating to open the second point in thecircuitI of this relay at armature |42, relay 66 falls back.v Thedeenergization of relay 66 results in the release of theI connectorswitch. Ground is removed from the circuit of the wiper cut-in relay atarmature 8|, and at armature 04 ground is removed from the test wiper|83 and therefore from the private normal conductor |1 and the releasetrunk conductor 51. Also at armature 86 the circuit of the releasemagnet |93 is completed. It will be seen; therefore, that as a result ofthe falling back of relay 66 the link circuit is released.

Considering now the eiect at the line circuit, when ground is removed`from the private normal conductor I1 the cut-off relay 5 falls back.'I'his connects up the line relay 6, which promptly energizes over theline, since the subscriber at station C has his receiver oif. Thefalling back of the cut-oi relay 5 opens the circuit of relay 4, butthisrelay is slow acting and it is held by the line relay 6 over a circuitwhich includes armatures and 8. Relay 4 keeps the start conductor 50clear of the ground which would otherwise be applied to it at armatureof the line relay, and it also maintains the winding of the cut-oilrelay 5 separate from the conductor 30 extending to the testbanks ofthefinders. The line is marked busy in the banks of the connectors byground applied to the test conductor |1 at armature |3 of the line relay6.

Talking battery is fed to the line through the windings of the linerelay 6, and the line equipment is therefore the only apparatus that isin use during conversation on a call of this character. The link circuitwhich was used to set up the con- It wil lbe renection has been restoredto normal as described tributor to step ahead and select lanother linkhave waited according to instructions for a long enough time to ring thedesired station several times and then he would have removed hisreceiver.

The operation of certain features of the invention which are disclosedin Fig. 3 will now be considered.4 The first feature which will beexplained is one which has' to do with the operatic of 'the relays 208and 209. 'I'hese relays are provided for the purpose of causing the nderdiscircuit in case the nder of the link circuit in use is unable to findthe calling line. This may happen from a variety of causes, forinstance, the Vtest wiper 52 of the `finder in the link circuitdisclosed in the drawings may be bent or otherwise out of adjustment sothatitdoes not properly 0- the circuit of relay 207i. Relay 201 fallsback and breaks the circuit of relay 206 and also the circuit of relay208. Relays 208, 209, and 206 accordclose the test circuit This willprevent the ilnder from stopping on the calling line. Obviously it wouldbe desirable to start another finder switch if such'A operation could beprovided for., y

When the start relay 207 pullsl up responsive to the grounding of thestart wire 5min addition to the operations which this relay performs inthe regular course, all` of which4 havebeen described hereinbefore, itprepares a circuit at armature 222 forrelay 209. 'I'he `referencecharacter P indicates a pulse machine which is assumed to becontinuously operating and which alternately grounds conductors 2M and2st. These applications of ground may be at fifteen-second intervals.YAssuming now -that for some reason or other the nder in use fails tostop on the calling line and therefore no ground is received back on/the conductor E. The rst time then that the pulse machine places groundon conductor 243' relay 200 will operate and. will close a lockingcircuit for itself at armature 225. Relay 208 closes at armature 22 acircuit for relay 209. Fifteen seconds later Vthe pulse machine groundsconductor 244 and relay 209 operates, locking itself at armature 22i'i.Relay 209 upon energizing closes a circuit at armature 226 for thestepping magnet 213 of the iinder distributor. The stepping magnetaccordingly energizes and breaks ingly deenergize. The circuit oi thestepping magnet '2|3 is therefore opened, the magnet deenergizes, andthe wipers of the nder distributor Aare therefore advanced one step. Asa result the inderI distributor is associated with the next linkcircuit. If the next link circuit is busy there will be a ground on theconductor such as 250, and as a result, therefore, relay 20 will beshort circuited and a circuit will be completed by way of armature 228and the interrupter contact of .the stepping magnet 2 I3 forautomatically operating the magnet 2|3 again so as to advance the wipersto the next link circuit. The nder distributor steps its wipers along inthis way until wiper 20| reaches a conductor such as 250 which is notgrounded, indicating that an idle link'cir- Acuit has been found. Thender distributor then comes to rest4 and relay 201, being no longershort circuited, again energizes. 'I'he nder switch of the newlyselectedlink circuit is then operated in the manner which has been heretoforedescribed in order to hunt for and connect up the y 1 1 calling line. Itwill be understood that the operation of the pulse machine provides aminimum interval of fifteen seconds within which the finder switchoriginally started locate and stop on the calling line, sending groundback on conductor 5 250. If this operation does not occur, the system isnot held up pending the replacement of the `receiver by the callingsubscriber, as would ordinarily occur, but the finder distributor isautomatically stepped ahead after the designated time Il0 interval inorder to select a new link circuit and start the nder thereof inoperation.

The so-called permanent lockout feature'of the system will next beexplained. `rI'he term permanent is customarily applied to a ss- 15tained calling condition on a line, which may be due to a receiver beingleft'oi the hook at some station on the line, or itl may be due to aground or short circuit on the line. When such a condition occurs, theline concerned will, o1 course, 2o be picked up by the finder switch ofan idle link circuit and the link circuit will await the receipt ofdiallingimpulses. If no dialling impulses are received the link circuitwould ordinarily be kept `out of service indefinitely. 'The linkcircuits are 25 provided on a percentage .basis and a few permanentstherefore would tie up all of the equipment in the system and preventother subscribers from setting up connections. In attendedexchangessupervisory signals are employed to notify the `attendant of theseconditions and the affected lines can be cut out of service so as 4tofree the switch-board equipment. In an unattended exchange, however, itis necessary to provide arrangements for taking care of these conditionswithoutthe assistance of an attendant. Such arrangements have'been knownbefore, but the one disclosed herein is believed to possess advantagesover-.anythat have been made heretofore. l 40 Forthe purposes ofexplanation it will be assumed that the line .associated with the linecircuit #i Fig. l, becomes grounded. This will operate the line relay Sin the usual manner, with the result that an idle .link circuit isappropriated for use through the medium of the finder distributor, Fig.3. The nder of the link circuit will locate the line on which thecalling condition is simulated,- and will establish connection theretopreparatory to the receipt of dialling impulses. So long as other linkcircuits remain in idle condition, so that if a genuine call is made inthe system a link circuit will be found available, nothing furtheroccurs as a result of the ground on I the line in question. The lineremains connected through to the link circuit. It will be understoodthat the condition maybe only temporary. Since a good many` of theseconditions clear themselves within a short time there is no usein'locking out the line or doing anything special so long as idle 6gtrunk circuits remain available for use. In the event that all the otherlink circuits become busy, however, it immediately becomes desirable tofree the link circuit which is being held by the permanent. l

When the link circuits all become busy, ground is removed from thecommon` conductor 254. Relay 240, therefore, drops back. As explainedbefore, relay 2|0 is normally energized and only falls back when all ofthe link circuits are taken into use. Upon deenergizing, relay 210 opensthe start .circuit in the finder distributor at armature 23|, and atarmature 228 it opens the automatic hunting circuit for the steppingmagnet 2 I 3. Relay 2|0 also closes at armature 230 a circuit for 75 ingon thesecond contact in its bank, which is connected to conductor 244,and no further operation takes place until the conductor 244 is groundedin due course by the pulse machine P. The motor magnet 242,thenadvancesthe switch another step, bringing the wiper 240 into engage,- nient withthe third Contact in its bank, which is 'connected to conductor 243. In`this way the timer switch `TS is stepped aheady at intervals until-eventually the wiper 24| arrives at the fourth contact in its bank,whereupon a circuit is completed for relay 2| I. armature 233, breaksthe circuit of the relay 2|2 at armature 234', and at armature 232 opensa point in the restoringcircuit for the timer switch.

Finally, at armature 235, relay 2|| disconnects ground from thesupervisory ground conductor 251 extending to all of the link circuits.Assuming that the link circuit shown in Figs. 1' and -2 is the one whichis being held by the permanent, the `removal of ground from thesupervisory ground conductor will result in the de energizati'on ofvrelays 65 and 66 and the link will be released. Ground is removedfromrelease trunk conductor 51 at the same time and the cut-oil relay. 5 inthe line circuit #I will fall back. Upon deenergizing relay 5 againconnects up the line relay 6 and this' relay'accordingly energizes dueto the ground on the line. Upon energizing, relay 6 closes a circuit atits armature vfor holding up relay 4 so that the latter relay remainsoperated notwithstanding .that its original circuit `is broken by thefalling back of the cut-oil relay. The line is made busy by theapplication of ground at armature |3 of the line yrelay to the privatenormal conductor I1.

It will be seen from the foregoing lthat the link circuit which-wasseized by the grounded line has been restored to common use and the'lline has been locked out by the holding up of relay 4. This relay keepsthe start wire 50 openfat armature 8, and at armature "I keeps thecut-off relay disconnected from vthe conductor 30 so as to prevent acalling condition being established in the banks of the nders. In theevent that the ground on the line should clear itself, the line relay 6will of course fall back and release relay 4. The line circuit isthereupon restored to nor'- mal condition so that if a genuine calloccurs on the line it can be handled in the usual way.

It will be noted also from the foregoing that no attention is paid topermanents unless all of the link circuits become busy. `'Ihus there maybe three or four permanents at one time and nothing will be done unlessthe link circuits are all taken into use. When this occurs, thesupervisory ground conductor is cleared of ground in the describedmanner and this releases all of the link circuits which are falselyAheld up by lines which are not actually in use. In fact, all the linkcircuits are released except those which are actually engaged inconversation. vIn this connection it should be pointed out that when'conversation is taking place on any link circuit,

Relay 2|| locks itself at- 1,999,1ss'- y I -the relay 'such as relay|03, Fig. 2, will be energiaed, and ground from the supervisory groundconductor will be replaced-by directground at such linli circuit. Thisinsures that the removal oi.- ground from the supervisory groundconductor. for the purpose of locking out permanents will not release alink circuit on which conversation is actually taking place. The timeinterval which is counted oli by the timer TS can be adjusted to suitthe ideas oi ditlerent operating companies l -by changing the wiring atthe banksof wiper 24|.

The operations which take place in setting up a connection to asubscriber in a distant exchange -will now be described. The tenth levelof theI connectors is reserved for one or more groups ci l trunk linesextending to distant automatic exchanges. For example, there may be agroup of four trunk lines extending from the exchange herein describedto some distant automatic exchange with which service is to` be given.It y there are other automatic exchanges the remaining six sets ofcontacts in the tenthlevel will provide facilities for one or moreadditional groups of trunks. There is nothing novel about the trunkcircuits which are and'accordingly reference is made to Patent No. I1,528,751, granted March 10, 1925, to Bellamy et al., for a disclosureof a trunk circuit and associated repeater which is suitable for thepurused-ior this purpose 25 pose. Since the present system includesgrounded lines the repeater F disclosed in Bellamy et al. is preferablymodified by placing the two line relay windings on separate cores, as isdone in the case of the connector, Fig. 2 of the instant application,reference being made to relays |00 35 and '|0|. 'I'he relay Iwhich isconnected to battery is the line relay. A A

It will be assumed that there is a group of four trunks terminated' inthe iirst four contact sets oi' the tenth level, each trunk extending 40by way of a repeater tothe distant automatic exchange, where itterminates in the usual incoming rst selector switch. Each trunk linelcomprises three conductors, the two line conductors and a testconductor. The two line conductors are, of course, connected in theupper and lower banks of the connectors. The test conductor or releasetrunk conductor is connected in the upper test bank of the connectors.That is, the bank which is associated with the wipers such as wiper V83of the connector shown. Only the first trunk line of the group isindicated in the, drawings. 'I'his trunk line comprises conductors 50|,502, and 503. Conductors 50| and,

503 are -the line conductors, while conductor 502 is the test or releasetrunk conductor. f

-Since a group of trunk lines is provided for handling calls to theautomatic exchange in question, the connectors such as the one shown inthe drawings must be arranged/to operate as rotary connectors.l This isan operation which is well understood, and merely means that thesubscriber in calling the distant exchange will dial the number of therst trunk line in the group. If this trunk line is idle it will beseized automatic rotary operation of the connector disclosed in thiscase are very similar to the circuits which are illustrated in thepatent to Wicks, No. 1,644,968, granted October l1, 1927. It will not benecessary,` therefore,` to explain the arrangement in great detail. Itmay b e stated that n the wiper m' or the-,connector is an additionalwiper which is provided for use in'controlling the automatic rotarymovement of the switch and has no other function. All test contactswhich are accessible to wiper |84 are strapped to the corresponding testcontactsr whichV are accessible to wiper |83, except in the case of the`last test contact of each group. 'I'his means -that as regards thegroup of trunk lines under discussion, the first, second, and third testcontacts of the naught level which are accessible to wiper |84 will be'strapped to the first, second and third test contacts inthe naughtlevel which are accessible to test'wiper- |83. 'I'he fourth test contactaccessible to wiper |84, which belongs to the last trunk line of thegroup, is not strapped, and this provides for stopping the connector onthis last trunk line in the event that it is busy.

It will be assumed now that the subscriber at station A on the line4which is associated with line circuit #L Fig. 1, desires to extend aconnection to the distant automatic exchange. In order to accomplishthis the subscriber must dial a preliminary number 01, followed by theregular number of the desired subscriber in the distant exchange. Whenthe receiver is removed at station A, the heretofore describedoperations take place by means of which the line is picked up by an idlelink circuit. It will be assumed that the link circuit shown in Figs. 1and 2 is taken into use. When the subscriber dials the first digit ofthe number, ten impulses are transmitted to the vertical magnet |80 andthe shaft of the switch is stepped up until the wipers are opposite thetenth level. When the shaft reaches the tenth level, the level oifnormal springs LN1 and LN2 are closed. Springs LN connect up the testwiper |83, while springs LN1 prepare a circuit for the switching-throughrelay |04.

The subscriber may now dial the digit 1. As a result the rotary magnet|8| receives one impulse of current whereby the connector shaft isrotated one step and the Wipers |82 to |85, inclusive, are brought intoengagement with the rst set of contacts in the tenth level. Relay |08 isenergized in parallel with the rotary magnet |8|, as describedhereinbefore and closes a circuit for relay |09. Only the functions ofthese relays which have to do with the automatic rotary movement will bedescribed at this time. Upon energizing relay |09 closes a circuit fromthe grounded release trunk conductor 51 by way of armature |52, thelevel olf normal springs LN1 and the lower winding of theswitching-through relay |04 to battery. The lower winding of relay |04is an ineicient winding and consequently the relay is only partlyoperated, just' sufficient to close the contacts labeled X in thedrawings. The closure of the contacts X by armature 125 completes acircuit which extends from the grounded release trunk conductor 51 byway of back contact of armature |32 of the busy relay |05, contacts X,upper winding of switchingthrough relay |04, and the lower winding ofsaid relay to battery. The upper Winding of relay |04 is, however, at.this time short circuited due to the operation of relay |09 andconsequently nothing further happens.

At the end of the directive rotary movement of the switch, relay |08falls back, and closes a circuit for the busy relay |05. If the rsttrunk line is busy the'busy relay |05 will operate from ground on thecontact engaged by wiper |83, and at armature |3| connects up theauxiliary test wiper |84. Since the two rst test contacts are strappedtogether, wiper 184 will also find ground and a circuit will becompleted by way of the said test wiper |84, armature |5|, armature |8|,contacts controlled by armature |51, armature |62,v interrupter contactof the rotary magnet |8|, and the winding of relay ||0 to battery. Relay||0 accordingly energizes, at armature |51 completes a locking circuitfor itself, and at armature .|99 completes a circuit for* the rotarymagnet which extends from ground at armature 8|, by way of armature |60,armature |99, and the winding of the rotary magnet |8| to battery. Uponenergizing, the rotary magnet |8| advances the switch wipers on to thenext set of contacts, and at the same time breaks the circuit of relayH0. The relay accordingly falls back and breaks the lrotary magnetcircuit. If ,the next set of contacts is busy the same operation will berepeated, and the rotation of the switch will continue until an idletrunk line is reached. It will be observed that relay |09 is connectedin parallel with the rotary magnet |8| by way of armature |45, armature|49, armature |44, and armature |64, so that while impulses are beingtransmitted to the rotary magnet as described in the foregoing, theseimpulses also are received by relay |09 and serve to maintain itenergized.

If all of the trunks are busy the rotation-Will continue until the lasttrunk line of the group is seized at which time the auxiliary test wiperWill find no ground potential due to the fact that the two test contactsassociated with this trunk are not strapped together. Accordinglyrotation of the switch will cease and the busy relay |05 will lockitself energized following the deenergization of relay |09, transmittinga busy signal tothe calling subscriber in the manner heretoforedescribed.

It will be assumed now that some trunk line is found to be idle, and forconvenience this will be taken as the first trunk line of the group, theone indicated in the drawings. When the relay |08 falls back then attheend of the directive rotary movement of the switch the test wiper |83will not nd ground and no circuit will be completed for the busy relay|05. Relay |85, accordingly remains deenergized. An instant later relay|09 t falls back and at armature |52 removes the shunt from the upperwinding of the switching-through relay 100. Relay |04 thereforecompletely energizes. As a result, test wiper |83 is connected to therelease trunk conductor 51 at armature |98. This immediately placesground on the test contact of the selected trunk to make it busy. Inaddition, the talking circuit conductors 55 and 56 are connected throughdirectly to wipers |82 and |85 of the connector, exclusive of therepeating Acoil windings and all connections to battery and ground.Relay |04 also,y opens the release circuit at armature |28, and atarmature |21 it opens the supervisory ground circuit so as to preventclosing the impulsing circuit when the lock-pulse relay 64 falls back. l

The calling line has now been extended by way of wipers |82 and |85 andtrunk conductors 50| and 503 to the repeater. The line relay of therepeater accordingly energizes and closes a circuit for the releaserelay. Upon energizing the release relay grounds conductor 502 and thisprovides holding ground for maintaining the relay 04 ofy the connectorin operated position. The'test wiper |83 has already been joined to therelease trunk conductor 51, as described, and ground is thereforesupplied for holding up the relays and 5 also. It is understood thatthis ground is fed back from' the repeater before the release relay 05of the connector has had time to fall back.

It will not be necessary to describe in detail the operation of theautomatic switches in the distant automatic exchange. Sufiice it to saythat when the digits of thesubscribers number are called, correspondingseries of impulses are repeated by the repeater in the trunk line andserve to operate the necessary automatic switches in the usual manner tocomplete the connection. When the subscribers are through talking theywill hang up their receivers and the replacement of the receiver at thestation A will bring about the deenergization of the line relay of therepeater. On falling back, the line relay breaks the circuit oftherelease relay and this relay therefore deenergizes to unground therelease trunk conductor 502. The apparatus is therefore restored tonormal in a manner which will be readily understood.

The trunk circuit shown in Fig. 5 will now be described. The communityexchange, to which this invention relates, may be trunk connected with amanual exchange as well as with an automatic exchange, and the trunkcircuits for connecting with the manual exchange may be -of the typeshown in Fig. 5. Itwill be assumed that there is a group of these trunkswhich extend from jacks such as J at the manual exchange in question andline equipments in the C. A. X.`similar to the line circuit #L Fig. 1.The normal conductors associated with the line circuits may be multipledin any level of the connector banks except the tenth level, which isreserved for switching through to 'automatic trunks as has beendescribed hereinbefore. Preferably, however, these manual trunks shouldnot be terminated in the sixth level as this level is set aside for theuse of large party lines. Any other level, as for example, the fifthlevel, will serve the purpose. 1n the case of the trunk circuit shown inFig. 5, therefore, it will be understood that jack J is located at theswitchboard in the distant manual exchange. The conductors 432, 431 and433 extend to a line equipment which is the same as the line circuit #LFig. 1. The normal conductors 435, 431, 438, and 439 extend to theconnector banks and may be connected to the first set of contacts in thefifth level, where they are accessible to wipers |82 to |85,respectively.

For the purposes of the explanation, it will be assumed first that theoperator at the manual exchange desires to complete a connection to somesubscriber in the C. A. X. The operator will therefore insert thecalling plug of an idle cord circuit in the jack J. The cord circuit maybe of the Well known common battery type which is in common use. Uponinserting the plug in the jack a circuit is completed in an obviousmanner for the relay 40|, which energizes by current supplied from thecord circuit. Relay 40| is of high resistance and does not operate thesupervisory relay in the cord circuit. Upon energizing, relay 40|connects up the sleeve relay 403 at amature 4|0. Relay 403 operates andlocks itself to the sleeve of the jackvat armature 4|3. Relay 4| 3 alsoprepares locking circuits for relays 405 and 406 at armature 4|4, and atarmature 4|6 it disconnects the ring-down relay 404 from in bridge ofthe trunk. At the front contact of armature 4|6 the lower trunkconductor 433 is extended to the lower right hand winding of therepeating coil, with the result that a loop is completed which includesthe polarized relay 402.

Upon the completion of the loop circuit in the manner described above,the line relay of the associated line equipment at the C. A. X. operatesin the usual manner and through the medium of the iinder distributor anidle link circuit is taken into use. Assuming that the link circuitshown in Figs. 1 and 2 is the one selected, the finder willjoperate inthe usual manner to -connect the link circuit with the tnmk line overwhich the call has been received. 'I'he line relay |00 of the linkcircuit is therefore energized over the loop in series with thepolarized relay 432 at theoperators position. The direction of currentiiow at this time is suchl that the polarized relay 402 is not operated.

The operator will now throw the dial key K so as to connect her callingdevice across the trunk line conductors 432 and 433, the calling devicebeing substituted for the bridge including the repeating coil andpolarized relay 402. 'I'he operator will now operate the calling devicein accordance with the digits of the required number. When the callingdevice is operated the first time a circuit is completed for relay 403,which energizes and locks itself at-armature 420. The operation of thecalling device is effective to control the. connector and the codeselecting-switch CS in the manner heretofore described so as to connectwith and signal the desired called subscriber. On completion of thedialling operation, the operator restores the key K, so that thepolarized relay is again included in the loop circuit which extends overthe tnmk to the C. A. X.

When the called subscriber answers relays Il, |03 and |01 operate ashereinbefore described, and the latter relay stops the signallingoperation. Relay |03 reverses the direction of current flow over thetrunk, operating the polarized relay 402. Upon energizing relay 402connects the upper winding of relay 405 in shunt with relay 40| atarmature 4||, and since the upper winding of relay 405 is of relativelylow resistance the supervisory relay in the cord circuit now operates,extinguishing the supervisory lamp. 'Ihis informs the operator that thecalled party has answered. Conversation between the party at the manualexchange and the local C. A. X. subscriber may now take place in theusual manner. When the subscribers are through talking they hang uptheir receivers and the supervisory lamps are accordingly lighted at theoperator's cord circuit. The calling supervisory lamp is lighted by thefalling back of the polarized relay 420, which'is brought about by thereversal of the current back to normal by the falling back of the relay|03 of the connector. 'Ihis latter relay, of course, restores undercontrol of relay 63 when the called man hangs up his receiver. Onobserving the lighted supervisory lamps, the operator will pull down theconnection and the equipment at the C. A. X. is restored to normal inthe usual manner.

A call which is extended from a calling subscriber in the C. A. X; to asubscriber in the manual exchange will now be considered. It will beassumed for this purpose that the calling subscriber is the subscriberat station A. The number which is to be called is number 511, ,which Ycorresponds with the previously describedconnection of the trunk linesin the connector banks. The final digit 1 of the number, it may bementioned, is determined bythe fact that it is desired to use individualline ringing for signalling over the trunk line rather than some codering.

When the receiver is `removed at station A a link circuit is taken foruse in the manner p reviously described. It will be assumed that thelink in Fig. is terminated. The connector wipers |82 to |85, inclusive,are therefore in engagement, respectively, with bank contacts to whichnormal conductors 436 to 439 are connected.

Upon dialling the lastl digit of the number, the digit 1, thecodeselector CS is operated one step, and the ringing circuit is connectedup to the individual line ringing conductor 339, Fig. 4. The trunk lineis now tested in the usual wayand assuming that it is found to be idle,the connector seizes it in the usual manner and the ringing operation isstarted. These operations have alreadyv sociated with the jack J, thusnotifying the operator that a call has been received over the trunkline. The operator therefore plugs into the trunk with an idle cordcircuit in order to answer the call. When the plug is inserted in thejack J relay 40| operates and connects up the sleeve relay 403. Relay403 operates and locks"I itself to the sleeve at armature 4|3. At theback contact of armature 4|4 relay 403 unlocks the ringup relay 404,which accordingly deenergizes and puts lout the call lamp. At the frontcontact of armature 4|4 relay 403 prepares a locking circuit for relay405. At armature 4|5' relay 403 prepares a circuit which will shortly bedescribed, and at armature 4|6 it bridges the right hand winding of therepeating coil and the polarized relay`402 across the conductors of thetrunk. The loop circuit is thus closed and relays 62 and 63 of theconnector are accordingly energized, these two relays feeding current tothe trunk circuit in the usual manner. Relays |03 and |01 are alsoenergized, the latter relay stopping the ringing operation. It will beobserved that the normal conductors 436 and 439 are reversed between theline circuit equipment and the connector banks sothat the current flowover the trunk line is now in the proper direction to operate thepolarized relay 402. This relay accordingly energizes and at armature 4|connects the upper winding of relay 405 in shunt with relay 40|. 'I'hisoperation controls the `supervisory lamp in the cord circuit in themanner previously described. The operator will now speak to the c allingparty and ascertain his wants, after which the desired connection iscompleted manually by inserting the other end of the cord circuit in thejack of the desired line.

It will be assumed now that the wrong number has been obtained or thatfor some other reason the subscriber at station A desires to recall theoperator. In order to do this the subscriber ashes his switch-hook,which means that he depresses `it momentarily a number of times.

When the receiver hook is depressed, the calling line circuit is brokenand the relay |00 falls back, followed by lock-pulse relay 64. Relay 64,upon .deenergizing, breaks the connection of relay 63 to the'upper'wlper|82 ofthe connector. This opens up the battery feed circuit over whichlcurrent has been supplied to the trunk through relays 63 and 62 inseries, holding up the polarized relay 402 at the'manual exchange. Whenthel circuit is broken in this manner, relay 402 falls back and byopening its contact 4|| the shunt is removed from relay 40| and the lampin the operators cord circuit is lighted. At the same time relay 402closes a circuit which extends from battery by way of a resistance tothe back contact of armature 42| armature 4 9, armature 4|5, andarmature 4|2,'to the upper trunk conductor 432. From this point thecircuit extends by way of normal conductor 439 and the lower connectorwiper |85 to relay 62, which is thus held in energized position. Relay62 may be slightly slowacting so as not to fall back when its initialcircuit is broken. However, it will do no harm if this relay falls backmomentarily. When relay 63 falls back, a circuit is completed whichextends from the supervisory ground conductor by way of armature 13 ofrelay 63, armature 1| of relay 62, and the winding of release relay 65to battery. Release relay65 is accordingly held energized so as to holdup the link circuit and prevent the con-` nection being released,notwithstanding that the hook-switch is depressed at the callingstation.

When the hook-switch rises at the calling station relays |00 and 04 pullYup again, a circuit having been prepared for the latter relay atarmature 12 of relay 62, and the latter relay again connects up relay63, thus reclosing the circuitjor supplying `current to the trunkcircuit over the connector wipers. Relay 402 is accordingly energizedagain and at armature' 4|| relay 40| is shunted down again to put outthe lamp at the operators cord circuit. Relay 402 also removes batteryfrom the upper trunk conductor 432. Relay 62 now holds up in series withrelays 63 and 402 as before. These operations may be repeated Vseveraltimes as the subscriber flashes his switchhook in the Well known manner,resulting in the interrupted operation of the supervisory lamp in theoperators cord circuit to notify her that her attention is required.

In view of the arrangements for recalling thel ceiver, the describedoperations result in the light ingof the supervisory lamp at theoperators cord circuit, and since the lamp 'remains lighted steadily theoperator will understand that the parties are through with theconnection. She will, therefore, remove the plugs from the jacks. Whenthe plug is removed from the jack.J the sleeve relay 403 is deenergizedand at armature 4|5 the circuit by which holding battery is connected tothe upper trunk conductor 4 32 is broken. Thisfpermits relay 62 of theconnector to fall back and open the circuit of the release relay 65. Theother circuits of this relay have already been opened by the fallingback of the. line relay |00 and the lock-puse relay 64, so that therelease relay 65 now deenergizes. The other said pulse relay ondeenergizing, and means controlled over said stepping circuit fordeenergizing said pulse relay and causing the same to close said lockingcircuit.

2. In an impulse repeating arrangement, a line relay and a line overwhich it is energized, a pulse relay, an initial energizing circuit forsaid pulse relay closed by said line relay, a locking circuit for saidpulse relay, means for opening the said initial energizing circuit, saidlocking circuit being under control of said line relay whereby when theline relay d eenergizes responsive to the first interruption oi a seriesthe pulse relay will deenergize, a circuit in which impulses areproduced by deenergizations of said pulse relay, and means controlledover said circuit responsive to each impulse for re'operating saidApulse relay.

3. In combination, a circuit, a relay for closing said circuit ondeenergizing inorder to produce an impulse therein, means controlledover said circuit for reoperating said relay to terminate f the impulseeach time one is produced, and means including a line relay responsiveto a series of digital impulses for 'controlling the deenergizations oisaid first relay.

4. In an automatic switch, aline relay, a step? ping magnet, a pulserelay controlled at a fron-t contact of said line relay, and a circuitfor said stepping magnet controlled at a back contact oi said pulserelay.

5. In an automatic switch, a line relay energized when the switch isseized, a pulse relay initially energized responsive to the energizationof said line relay and deenergized responsive to the deenergization ofsaid line relay, means forI preventing said pulse relay from energizingwhen the line relay energizes the second time, a stepping magnet, acircuit for said magnet closed by said pulse relay upon deenergizing,and a circuit for energizing said pulse relay controlled by saidmagnet.' f

6. In'an automatic telephone system, a group of automatic switchesaccessible to calling lines, means whereby said. switches are seized andmade busy responsive to calling conditions on i said'lines, timingmeans, means for starting said timing means responsive 'to all saidswitches being in seized condition at the same time, and meanscontrolled by said timing means for restoring all'said switches tocommon use.

7.. A system as set forth in claim 6, characterized by the provision ofmeans which in the event that one of said switches is included in aconversational circuit at the time the restoration takes place willprevent the restoration oi such switch.

8. In an automatic telephone system, a plurality of automatic switchesfor extending calling lines, means for seizing one of said switches reisponsive to a calling condition on one of said lines, means for freeingthe seized switch ii dialling impulses are not received within apredetermined time, means for operating said last means only when all ofsaid switches are in use, and means for preventing the continuance ofthe calling condition on said line from causing the reseizure4 of thesame switcher the `seizure of another switch. Y i 9. In an automatictelephone system, a switch for use in connecting calling" and calledlines, al

relay which is energized responsive 4to the answering of a calledsubscriber, a conductor supplying holding ground to said switch, meansexternal to the switch for removing ground from said conductor, andmeans controlled by saidrelay. ior supplying a local ground to theswitch independent of said conductor so that if ground is removed ftherefrom during conversation the switch will not be released.

10. In an automatic telephone system, party lines, means includingconnector switches controllable over calling lines toconnect with calledlines, means whereby the subscriber on one oi said party lines can seizeone of said connectors and operate the same to connect with his ownline, means for givingthe callying party la busy signal, meansresponsive to the replacement oi the receiver at the calling station forgrounding the test wiper of the connector in use, thereby extendingholding ground to the release trunkof said connector by way oi theprivate normal conductor of the calling line, means for opening theincoming talking conductors to said connector while the same ismaintained `by said holding ground, means for signalling the calledsubscriber througha talking wiper of said connector, means for releasingthe connector when the calling or the called subscriber removes thereceiver, and means individual to the calling line for supplying talkingcurrent.

11. In a telephone system, a trunkline in coming to a connector switch,said trunk line trolled by said line relay for grounding said releasetrunk, a second slow-acting. relay in said switch energized by ground onsaid release trunk, a release magnet in said switch controlled by saidsecond relay, and means controlled by the replacement of the receiver onthe calling line when the switch is being used for a revertive call forgrounding said release trunk, whereby the said second relay is held upto maintain the switch operated after the line relay and the releaserelay have deenergized.

12. In an automatictelephone system, a connector switch, switchingmechanism for extending a calling line to said connector, a releasetrunk conductor extending between said `mecha` nism and the connector tohold the connection, a private normal conductor individual to thecalling line over which busyV potential is extended to the testbank ofsaid connector, said normal conductor being temporarily connected tosaid release trunk conductor, means for'operating said connector toselect a called line, and means responsive to the replacement of thereceiver at the calling line for grounding the test wiper of saidconnector if the called line was found busy, whereby if the called lineis also the calling line a ground potential will be extended by way ofthe private normal conductor to said release trunk conductor to preventthe release oi thev 4is busy, said busy relay preventing the normal.

operation of said seizing relay, and means respon-

